1. Field
This disclosure relates to signal processing.
2. Background
For applications in which voice recording (e.g., for communications) occurs in a noisy environment, it may be desirable to separate a desired speech signal from background noise. Noise may be defined as the combination of all signals interfering with or otherwise degrading the desired signal. Background noise may include numerous noise signals generated within the acoustic environment, such as background conversations of other people, as well as reflections and reverberation generated from the desired signal and/or any of the other signals. Unless the desired speech signal is separated from the background noise, it may be difficult to make reliable and efficient use of it.
The acoustic noise encountered in a typical use environment may include a variety of different components, such as music, sounds from interfering sources (e.g., a TV set, a radio, a competing talker), babble noise, street noise, and/or airport noise. As such noise is typically nonstationary and may have an average spectrum is close to that of the user's own voice, it may be hard to model using traditional single-microphone or fixed beamforming type methods. Therefore it may be desirable to use multiple-microphone-based signal processing techniques, such as spatially selective processing, to support separation of a speech component in noisy environments.
In some applications for voice recording, the location of the user's mouth relative to the microphone may change during use. For example, applications for voice communications are evolving beyond traditional telephony to include scenarios in which the user's mouth is located at some distance away from the audio sensing device during use. Examples of such scenarios include Voice over IP (VoIP) telephony using microphones (and possibly a webcam) embedded in a laptop or tablet computer. In such cases, movement of the user's mouth relative to the device may significantly affect the performance of a spatially selective processing operation.